Magnetic alloy



Patented May 13, 1952 7 2,596,705 MAGNETIC ALLOY Donald L. Martin, Ballston Lake, N. Y., assignor to General Electric Company, a corporation of New York No Drawing. Application September 27, 1950, Serial No. 187,157

6 Claims. 1 e

The present invention relates to a new and improved magnetic alloy. More specifically it is concerned with a magnetic alloy particularly useful in the fabrication of rotors for hysteresis dium and 6.1% nickel, balance iron. These alloys are characterized by good cold workability combined with a relatively high Br/Hc ratio and a coercive force between 50 and 100 oersteds.

motors. 5 Nickel within the critical range of from 5 to 7 A hysteresis motor may be defined as a type of percent is an essential component of the present synchronous motor without D. C. excitation, alloy and distinguishes it both magnetically and which starts by virtue of the hysteresis losses infrom the standpoint of composition from known duced in the rotor by the revolving magnetic cobalt-iron-vanadium alloys such as the alloy defield of the primary and operates normally at 10 scribed in Patent 1,862,559-White et al. With synchronous speed due to the magnetic rethese critical amounts of nickel and by holding tentivity of the rotor member. A typical rotor the vanadium content of the alloy within the construction is shown in Patent 1,768,386-Warprescribed limits, preferably about 4.4% by ren as comprising a continuous ring of magnetic weight, there is obtained a cold workable alloy material provided with an integral bar or bars which can be readily rolled to thicknesses as across the diameter. The ring cooperates with a small as 0.010" to provide a sheet or strip suitrotating magnetic field to produce the starting able for use in the stamping of hysteresis motor torque and the bar or bars produce a polar synrotor laminations, which cold rolled material by chronizing eifect to bring the rotor into and hold a suitable heat treatment can be given magnetic it in synchronism. In the construction shown properties including a residual induction of at in the Warren patent, the bar also serves as a least 12,000 gauss usually at least 14,000 gauss, spider for supporting the rotor member on the and a coercive force of from 50 to 100 oersted. motor shaft. In the practice of the present invention a melt In an ideal hysteresis motor, the hysteresis 0f t f u in r nt in t e sp fi pr p rtorque is constant at all speeds from standstill to 2 e s st d the asti g subjected to an elesynchronism. In other words the starting torque, v t d mp rature of about 1000 C. for a period pull-in torque and pull-out torque are an of time before hot rolling to a thickness of about mutually equal to one another. In practice, how- 0.1 inch. The brittle material obtained at this ever, it has not been possible to attain these ideal thickness is t a ealed at about 1000' C. conditions or even to approach them with the a d water q c pr o o c l rol g to a types of rotor materials presently available, finish thickness of about 10 mils. Rotor lamina- T present invention has t principal obje t tions are punched from the cold rolled strip. the provision of an improved magnetic alloy par- To v p the desired ic qu i i th ticularly adapted for t manufactur f hysterb resultant punchings are heat treated for a period Sis motor t of from 15 minutes up to an hour or more at a A further object of the invention is to provide per tu in e hbo hood of 600 C. a cold workable and heat treatable magnetic alloy After heat treatment r t r leminations of an characterized by a high residual induction Br y of Cobalt, nickel, 4.4% e eand a medium coercive force He in the range of dium, balance il'on except for incidental p ff0m50t 100oe13teds 40 ties exhibited B1- of 14,100 gauss and Ho of 90 It has been, found that these objects can be atoersteds and Ba HdMaX of 605,000. These rotor tained with an alloy essentially comprisin 43 members assembled into a standard hysteresis to 47 percent by weight cobalt, 4 to 6 percent motor were torque tested and compared with a vanadium and 5 to '7 percent nickel, balance iron similar rotor composed of the magnetic material except for incidental impurities. A preferred currently employed for this purpose and known alloy is one containing 45.6% cobalt, 4.4% vanaas a 5% tungsten steel.

ti t at as a P6 1. 94 1. 94 1.39 1. as 1.21 1.41 1. 07 1.00 Sandvik torque.

Start is starting torque at non-synchronous speed. Pull In is starting torque at synchronous speed.

In the above table, the alloy of the present invention is designated as P6 and the currently used standard alloy as a 5.75% tungsten having a Br of about 10,500 and an I'Ic of about 60. The actual composition of the tungsten alloy is 5.75% tungsten, 0.68 carbon, 0.40 chromium, balance iron.

From the results set forth in this table, it will be seen that the alloy of the present invention provides higher torque values under all test conditions. It is also apparent that a hysteresis motor comprisin the alloy of the present invention approaches much more nearly the requirements of an ideal hysteresis motor. For example whereas the pull-out torque for the motor containing the tungsten steel rotor is more than twice the starting torque or the pull-in torque at 115 volts, the motor equipped with the alloy of the present invention had a pull-out torque which was only about 35% higher than the start ing and pull-in torques. At 92 volts the motor having a rotor composed of the alloy of the pres ent invention is characterized by pull-out starting and pull-in torques which were substantially the same.

These differences between the alloy of the present invention and the standard Sandvik alloy are attributable at least in part to the difierences in their Br/Hc ratios. The alloy of the present invention while being characterized by approximately the same coercive force has a Br value at least 2500 gauss higher than the tungsten steel.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A magnetic alloy comprising 5 to '1 percent nickel, 4 to 6 percent vanadium, 43 to 47 percent cobalt, balance substantially all iron, said alloy having a coercive force between 50 and 100 oersteds and a Br of at least 12,000 gauss.

2. A cold workable magnetic alloy comprising 5 to 7 percent nickel, 4 to 6 percent vanadium, 43 to 47 percent cobalt, balance substantially all iron except for incidental impurities.

3. The alloy of claim 1 containing 6.1% nickel, 4.4% vanadium, 45.6% cobalt, balance iron.

4. The alloy of claim 2 containing 6.1% nickel, 4.4% vanadium and 45.6% cobalt.

5. A rotor lamination for a hysteresis motor composed of the cold worked and heat treated alloy of claim 1.

6. A rotor lamination for a hysteresis motor composed of the cold worked and heat treated alloy of claim 3.

DONALD L. MARTIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,862,559 White June 14, 1932 OTHER REFERENCES Transactions A. I. M. 13.. vol. 188, February 1950, Journal of Metals. Published by the A. I. M. E., New York. Pages 287, 291, 292 and 293. 

1. A MAGNETIC ALLOY COMPRISING 5 TO 7 PERCENT NICKEL, 4 TO 6 PERCENT VANADIUM, 43 TO 47 PERCENT COBALT, BALANCE SUBSTANTIALLY ALL IRON, SAID ALLOY HAVING A COERCIVE FORCE BETWEEN 50 TO 100 OERSTEDS AND A B OF AT LEAST 12,000 GAUSS 